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How to Create A Self Signed Certificate

A self signed certificate is a certificate that is signed by the person creating it rather than a trusted certificate authority. Free self signed certificates can enable the same level of encryption as a $1500 certificate signed by a trusted authority, but there are two major drawbacks: a visitor's connection could be hijacked allowing an attacker view all the data sent (thus defeating the purpose of encrypting the connection) and the certificate cannot be revoked like a trusted certificate can. We're going to explain when a self signed certificate should and shouldn't be used and then share tutorials on how to generate a self signed certificate for common platforms like Microsoft IIS, Apache, and Java Keytool.

When to Use a Self Signed Certificate

Never use a self signed certificate on an e-commerce site or any site that transfers valuable personal information like credit cards, social security numbers, etc.

A certificate serves two essential purposes: distributing the public key and verifying the identity of the server so visitors know they aren’t sending their information to the wrong person. It can only properly verify the identity of the server when it is signed by a trusted third party because any attacker can create a self signed certificate and launch a man-in-the-middle attack. If a user just accepts a self signed certificate, an attacker could eavesdrop on all the traffic or try to set up an imitation server to phish additional information out of the user. Because of this, you will almost never want to use a self signed certificate on a server that requires anonymous visitors to connect to your site. In these cases, you really need to lay down a few bucks on a trusted certificate (there are plenty of cheap SSL certificates). However, self signed certificates have their place:

An Intranet. When clients only have to go through a local Intranet to get to the server, there is virtually no chance of a man-in-the-middle attack.

A development server. There is no need to spend extra cash buying a trusted certificate when you are just developing or testing an application.

Personal sites with few visitors. If you have a small personal site that transfers non-critical information, there is very little incentive for someone to attack the connections.

Just keep in mind that visitors will see a warning in their browsers (like the one below) when connecting to an server that uses a self signed certificate until it is permanently stored in their certificate store.

Self Signed Certificates In IIS

Creating a self-signed certificate in IIS 7 is much easier to do than in previous versions of IIS. IIS now provides a simple interface for generating a self signed certificate. One drawback, is that the common name of the certificate is always the server name instead of the site name. In order to change the common name, you'll need to follow some additional steps.